1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device wherein a MOS (Metal Oxide Semiconductor) structure and a semiconductor pressure sensor are integrated.
2. Background Art
In recent years, semiconductor pressure sensors are used in various fields including automobiles. An example of semiconductor pressure sensors is a semiconductor pressure sensor integrated on a CMOS (Complementary Metal Oxide Semiconductor) circuit. A CMOS integrated pressure sensor is proposed which aims to achieve further size reduction, lower cost and higher accuracy (e.g., see Japanese Patent No. 4267322)
In this conventional semiconductor pressure sensor, a region in which a CMOS circuit is formed (MOS region) and a region in which a pressure sensor is formed (pressure sensor region) are defined on a semiconductor substrate. In the MOS region, a CMOS circuit is formed which includes an n-channel type MOS transistor and a p-channel type MOS transistor. In the pressure sensor region, a capacitative pressure sensor is formed. In the capacitative pressure sensor, a fixed electrode and a movable electrode are formed, and a vacuum chamber is provided between a fixed electrode and a movable electrode. The vacuum chamber is sealed with a sealing film. The pressure is measured by detecting a change in the distance between the movable electrode and the fixed electrode as a change in the capacitance value.